The present invention concerns an escapement device for a timepiece.
For a timepiece and particularly a mechanical timepiece, the escapement device constitutes a master part which, on one hand, has to deliver the power required to maintain the oscillatory motion of the mechanical oscillator, balance wheel, and hairspring, and on the other hand, must transmit the oscillation frequency of the oscillator to the gears driving the time display.
Thus, the prior art in devices of this type is considerable. The handbooks published under the titles xe2x80x9cEchappements et moteurs pas à pasxe2x80x9d (Escapements and step motors) and xe2x80x9cThxc3xa9orie d""horlogeriexe2x80x9d (Watch-making theory), ISBN 2-940025-10-X, both by the Swiss Federation of Technical Colleges, describe numerous escapement devices, and in particular those called xe2x80x9canchorxe2x80x9d, xe2x80x9cdetentxe2x80x9d, and xe2x80x9cGrahamxe2x80x9d escapements.
The major drawbacks of these known devices are:
a poor efficiency; the best efficiency that can be obtained with these known devices is of the order of 30 to 40%, which limits the running time of the watch,
a limited working frequency; the efficiency of the known escapements drops off considerably when the oscillator frequency is raised to a perceptible degree, and moreover, anchor escapements develop a wear problem of the escapement wheel when the frequency is high,
difficulties of manufacture; for efficiencies of the order of 30 to 40%, the anchor escapements require a number of highly precise trimming operations.
It is a goal of the present invention, therefore, to propose an escapement device for a timepiece that is improved over known devices, that is, their known drawbacks have been reduced at least in part.
It is another goal of the invention to propose an escapement device that is insensitive to external impacts, and will not exhibit galloping effects.
It is yet another goal of the invention to propose a timepiece equipped with such an escapement device.
These goals are attained by an escapement device for timepieces as described in claim 1, as well as by a timepiece as described in claim 19. Particular embodiments or variants are described in the dependent claims.